Consider the following relation definition:
STUDENT(
Student_Number: integer NOT NULL
Name: variable length character string length 20 NOT NULL)
Primary Key Student_Number
HOUSING(
Housing_ID: integer NOT NULL
Student_Number: integer NOT NULL
Building: variable length character string length 25 NOT NULL)
Primary Key Housing_ID
Foreign Key Student_Number References
STUDENT(Student_Number)
ON DELETE NO CHECK
ON UPDATE
Which integrity constraint is violated in this relation definition?
A.
Entity integrity
B.
Domain constraint
C.
Referential integrity
D.
Enterprise constraint